The energetics of interaction between oxygen vacancies in sillimanite: A model for the mullite structure

✍ Scribed by S. Padlewski; V. Heine; G. D. Price

• Publisher: Springer-Verlag
• Year: 1992
• Tongue: English
• Weight: 742 KB
• Volume: 19
• Category: Article
• ISSN: 0342-1791
• DOI: 10.1007/bf00202108

✦ Synopsis

A microscopic model is introduced to discuss the modulated structure of mullite. The oxygen vacancies of this aluminosilicate are known to play a central role. In particular, a single vacancy strongly orders its surrounding A1/Si tetrahedral sites. It is shown in this work that if two oxygen vacancies approach too closely to one another, their A1/Si "dressing" overlap. This situation results in repulsive interaction. The field of interaction between the vacancies is estimated with the use of an atomistic computer simulation. We use a Bragg-Williams type of theory to dicuss the ordering pattern of the vacancies. Due to "frustration" between the two dominant repulsive interactions, our model predicts a modulated phase transition in agreement with observation.